Supplementary Material for: Skin-Homing IL-13-Producing T Cells Expand in the Circulation of Patients with Drug Rash with Eosinophilia and Systemic Symptoms

<p><b><i>Background:</i></b> Drug rash with eosinophilia and systemic symptoms (DRESS), also known as drug-induced hypersensitivity syndrome, is characterized by severe drug-induced reactions with extensive cutaneous lesions and visceral involvement. Although T cell-mediated hypersensitivity reactions to drugs may be involved in the pathogenesis of DRESS, there is limited data regarding the T-cell phenotypes responsible for the pathogenesis of DRESS. <b><i>Objective and Methods:</i></b> Using flow cytometry, we investigated the cytokine profiles and cutaneous lymphocyte antigen (CLA) expression in circulating T cells in patients with DRESS. <b><i>Results:</i></b> The proportions of circulating IL-4- and IL-13-producing CD4+ T cells, but not CD8+ T cells, were significantly higher in patients with DRESS during the active stage of the disease than in healthy subjects, and these proportions declined during the recovery stage. No differences in the proportions of circulating IFN-γ-, IL-17-, and IL-22-producing CD4+ and CD8+ T cells were observed between patients with DRESS and healthy subjects. A strong correlation between the proportion of IL-13-producing CD4+ T cells and serum levels of thymus and activation-regulated chemokine was observed. The proportion of CLA-expressing CD4+ T cells was significantly higher during the active stage of the disease. Moreover, the proportion of IL-13-producing CD4+ T cells was higher in the CLA+ subset than in the CLA- subset. <b><i>Conclusions:</i></b> Skin-homing IL-13-producing CD4+ T cells may be involved in the pathogenesis of DRESS.</p